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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 5th May 2020, 10:42 pm   #41
Timbucus
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Default Re: Good review of SC/MP.

Also I am also not sure now that IC11 is a 74C04 as you suggest as you can clearly see two patch wires from the marked W and R and I think they snake across the board to use pins 1 and 2 which would be the first Hex inverter on a 7404... Still you can do the same with shorting out the two inputs to a NAND gate so that is also a valid solution and means that IC2 and IC11 - stay in their own areas - the diagram I posted above began to reflect that element of doubt.

Edit - actually that is more likely that IC11 is a 74C00 and the W and R wires running from Pin 1 and 2 on the CPU are going to pin 1 and 2 on IC11 which are the inputs to a NAND gate in that chip... so ignore the above...

Last edited by Timbucus; 5th May 2020 at 11:06 pm.
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Old 5th May 2020, 10:59 pm   #42
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Default Re: Good review of SC/MP.

Quote:
Originally Posted by philoupat83 View Post
the schemat does not work on multisim c is why I proposed this slow modification is a clock 1 hz for debugging
and step an advance not a multisim confirms it
OK - I built that bit of the circuit on the breadboard and was wondering how the single step worked - thanks for clarifying. That must be a mistake in the DJD article.
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Old 6th May 2020, 1:06 pm   #43
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Default Re: Good review of SC/MP.

hello thank you for clarification regarding IC11 BIWOOD to wanted to make low cost
with you we will surely come to understand this circuit.
I think that the operating plan of the electronic practical SCRUMPI is wrong on many points it does not use the CONT input while on all the other kit sc/mp this pin is used ELEKTOR MINISCAMP INTROKIT(SC/MP Technical Description fig 2-8 page 2-9) I will do a simulation by scanning the NHOLD pin by simulating with a switch NADS
NHOLD is I/O ? hard for a Frenchi to read the English datasheet but I count on you to help me thank you very much
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Old 6th May 2020, 5:28 pm   #44
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Default Re: Good review of SC/MP.

Quote:
Originally Posted by philoupat83 View Post
hello thank you for clarification regarding IC11 BIWOOD to wanted to make low cost
with you we will surely come to understand this circuit.
Yes I hope so it is nice to be working on this again with someone who is as interested as I am!

Quote:
Originally Posted by philoupat83 View Post
I think that the operating plan of the electronic practical SCRUMPI is wrong on many points it does not use the CONT input while on all the other kit sc/mp this pin is used ELEKTOR MINISCAMP INTROKIT(SC/MP Technical Description fig 2-8 page 2-9) I will do a simulation by scanning the NHOLD pin by simulating with a switch NADS
NHOLD is I/O ? hard for a Frenchi to read the English datasheet but I count on you to help me thank you very much
I suspect CONT is just held HIGH on SCRUMPI as it is used to pause after the full instruction cycle but, the SCRUMPI uses the NHOLD (an input only) as its method to allow you to see the address and data bus LED's during each micro-cycle rather than the whole set of cycles that make up an instruction.
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Old 6th May 2020, 8:00 pm   #45
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Default Re: Good review of SC/MP.

yes this topic is interesting attached two NS document
NHOLD as WAIT CONT as START/STOP
I simulate the circuit but I do not understand the Q output of the 7474 did not react
Attached Files
File Type: pdf SCMP_Timing.pdf (1.86 MB, 10 views)
File Type: pdf sc_mp single cycle control.pdf (972.2 KB, 9 views)
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Old 7th May 2020, 11:15 am   #46
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Default Re: Good review of SC/MP.

Do you mean you simulated the NS diagram you posted with the more complicated Single Instruction and Single Cycle options or the simple three chip one on the SCRUMPI? I had the same problem when I built the circuit but, I think this is related to the fact that you need to simulate the NADS and the D7 interrupt flag - just waiting for my 500 and I think I will just build it!
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Old 7th May 2020, 3:44 pm   #47
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Default Re: Good review of SC/MP.

yes I tried several solutions with mutisim
I do not understand all what is the role of slow I simulate NADS and D7 with positions HIGT and LOW
he must make a real model or have the original circuit
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Old 7th May 2020, 4:22 pm   #48
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Default Re: Good review of SC/MP.

SLOW should act as if STEP is being pressed slowly, probably about once every second.
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Old 7th May 2020, 5:13 pm   #49
Timbucus
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Default Re: Good review of SC/MP.

Yes exactly - I could not get it to work as in the DJD diagram which shorts PIN 2 to Ground - this one (my current working diagram) actually does work on the breadboard as SLOW just shorts the PINS of the STEP switch really and forces the 555 into a permanent astable. Click image for larger version

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Old 7th May 2020, 5:18 pm   #50
philoupat83
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Default Re: Good review of SC/MP.

yes the ne 555 produces pulses of 1s to be able to debug the program
but the output of the toggle D must change all the 1s but in multisim this does not do I will make a real model
RUN allows high threshold of NHOLD and HALT create a break
I seek to understand D7 and NADS
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Old 7th May 2020, 5:21 pm   #51
Timbucus
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Default Re: Good review of SC/MP.

On the circuit I built SLOW just permanently connects the 2 and 6 PINS together so the system runs as a 1Hz ASTABLE. When not in SLOW mode the STEP button just allows one or more astable vibrations while held down.

When you pointed out why that did not work I realised that SLOW is just a permanent short of STEP. See the amended diagram above - I changed the EARTH connection to be a wire to the top of the CAP on pin 6. This now works as I would expect generating a steady stream on SLOW or a single pulse using STEP when SLOW is nit selected.

The RUN/HALT side of the 7474 makes R (the HALTFLAG) to be dependent on the D7 value when NADS is asserted.

I.e.

Code:
RUN/HALT  NAND1  NAND2            HALTFLAG

D7           H/L     /NADS       H on NADS so halts each cycle
N/C         H        /NADS       H/L depends on the 555 pulse generator
GND          L      /NADS        H - so no halts on the processor
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Old 7th May 2020, 5:26 pm   #52
Timbucus
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Default Re: Good review of SC/MP.

Quote:
Originally Posted by philoupat83 View Post
yes the ne 555 produces pulses of 1s to be able to debug the program
but the output of the toggle D must change all the 1s but in multisim this does not do I will make a real model
RUN allows high threshold of NHOLD and HALT create a break
I seek to understand D7 and NADS
NHOLD is an input to the CPU which pauses mid cycle while held LOW
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Old 7th May 2020, 6:18 pm   #53
philoupat83
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Default Re: Good review of SC/MP.

Iím doing your circuit and I donít think itís working youíre just replacing SLOW with STEP. step should not generate pulses but a single pulse . slow I agree genere impulses at 1HZ
see my diagram I still canít get the D toggle to work properly for the circuits I agree on your choices
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Old 7th May 2020, 6:22 pm   #54
philoupat83
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Default Re: Good review of SC/MP.

le rappart cyclique est determinť par le rapport R1 R2 .
C doit etre 1ĶF
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Old 7th May 2020, 7:10 pm   #55
Timbucus
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Default Re: Good review of SC/MP.

I am also struggling to get the 7474 working on my breadboard version - I must be missing something... as it is a D type it should trigger only on the leading edge so I wonder as the output is high and pulsing low the Flip Flop is not triggering.
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Old 7th May 2020, 8:20 pm   #56
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Default Re: Good review of SC/MP.

my problem comes from multisim
it is necessary to be able to replace NADS by a pulse generator I think that at the end of the cycle NADS returns a signal hight or low that makes change of state the toggle we have the good schemat slow step halt run
have approached the final schemat I will check the schemat PROTECT LOAD
have approached the final schemat I will check the schemat PROTECT LOAD
we are almost at the end also remains the layout of the latches and I think that to reduce the current in the drivers we could use a serial LED on the common LED
halt is a break with D7 I donít understand the whole explanation
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Old 7th May 2020, 8:40 pm   #57
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Default Re: Good review of SC/MP.

diagram of ne555
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Old 9th May 2020, 12:43 pm   #58
philoupat83
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Default Re: Good review of SC/MP.

hello
I hope everything is right for you
a timbucus and slothie
your plan seems to me except for the potential of step that must be positive at rest
I started creating the SCRUMPI schema on eagle
I still have some things to do with you.
load and protect operation does not seem to me to be correct
we must redefine the resistors (location values)
you noticed the number of pine latch 74c173
can be an intention to use 74c175? 5miniscamp)
on the article there are 16 pin on sunmoonstar 14 pin
attached a diagram to be corrected
it is necessary to redefine the gnd potential and connect to the load and protect switches
the sitch are it simple or momentary for step reset load why three position for run halt
Attached Files
File Type: pdf scrumpi diagramme Model (1).pdf (105.0 KB, 11 views)
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Old 9th May 2020, 2:14 pm   #59
Timbucus
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Default Re: Good review of SC/MP.

Quote:
Originally Posted by philoupat83 View Post
hello
I hope everything is right for you
a timbucus and slothie
your plan seems to me except for the potential of step that must be positive at rest
Well thanks - I still cannot get the breadboard built machine to work well the output Q of the flip flop stays on!

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The resistor is missing on the LED as it pulled off with my scope lead - in case anyone spots the 'obvious' reason the LED will not light up!

Quote:
I started creating the SCRUMPI schema on eagle
I still have some things to do with you.
load and protect operation does not seem to me to be correct
we must redefine the resistors (location values) ... it is necessary to redefine the gnd potential and connect to the load and protect switches
Which resistors do you think are wrong?

I have been looking at how the PROTECT and LOAD works as well - the protect must just interrupt the ability to use LOAD but, there must also be a connection to the RAM R/W from the CPU as well somewhere...

Nice one drawing in Eagle - I have carried on with my prototype board build - I was going to add sections as we get them working.

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Quote:
you noticed the number of pine latch 74c173
can be an intention to use 74c175? 5miniscamp)
on the article there are 16 pin on sunmoonstar 14 pin
attached a diagram to be corrected
I am sure it is a 74C173 as that is said in the adverts in several places
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it is just thesunmoonstar has different 14 pin chips in the 16pin sockets - he seems to have modified it quite a bit. In any case they are not critical for operation as they have some jumpers for them to be used as IN or OUT.

Quote:
the sitch are it simple or momentary for step reset load why three position for run halt
I mentioned my thinking above for this: H on NADS so halts each cycle, H/L depends on the 555 pulse generator when GND so no halts on the processor just runs - see the earlier table for details.
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Old 9th May 2020, 4:11 pm   #60
philoupat83
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Default Re: Good review of SC/MP.

it is not an eagle plan but an implementation to define the pcb with autodesk for eagle I create the symbols ISP8A/500d and MM211
attached plan of simple feeding in the philosophy BIWOOD
the plan is in progress
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